ITRM960172A1 - PROCESS FOR COATING A SUBSTRATE WITH AN EC COMPOSITION = MENTION AND ADDITIVE COMPOSITION USED THERE. - Google Patents

Description

DESCRIPTION

accompanying a patent application for an invention entitled "Process for coating a substrate with a cementitious composition and additive composition used therein"

This invention relates to the spray distribution of cementitious compositions and mixtures used therein.

The oldest and by far the most widely used evaluation of the workability of a cementitious conglomerate or mortar is the settling test, defined in ASTM C143. A truncated cone-shaped mound is shaped on a table and then the template or mold is removed, the trim being the difference in height on the table between the top of the original template and the level to which it descends. The larger the trim, the better the workability.

In the case of spray distributed concrete, sometimes also known as "shotcrete", it is highly desirable for a concrete to be pumpable (a condition that requires considerable settling), but when it is sprayed over a substrate, it becomes very quickly rigid (a condition that almost does not allow for trim). A system for achieving this objective is described in the Published PCT Application WO 94/02428, characterized in that a two-component mixture is used, one component being added in the mixing phase and the second just before final use. In the case of the spray-distributed cement conglomerate, the second component is added to the nozzle from which the cement conglomerate is sprayed. In the case of the spray-distributed cement conglomerate, an accelerator is also used, the accelerator being added in a conventional manner (to the nozzle) and being selected from the conventional accelerators.

It has now been found that a combination of the two component blend previously described here and a particular accelerator provide unexpectedly good results. Accordingly, in accordance with the present invention, a process is provided for coating a substrate with a cementitious composition, a process which comprises the preparation of a hydraulic cementitious mixture and its application on a substrate by means of spraying through a nozzle, being added to the mixture one component of a two-component mixture, the other component being added to the nozzle, the components being a condensate of β-naphthalene sulfonate-formaldehyde (BNS) and a water-soluble poly (alkylene oxide) of molecular weight (average weight) from 100,000 to 8,000,000 {"PAO"), an accelerator being further added to the nozzle which is chosen from the group consisting of aluminum sulphate, aluminum hydroxide and aluminum hydroxy sulphate ("compound based on aluminum ").

In a. further embodiment of the invention the aluminum-based compound constitutes a part of the component added to the nozzle.

In still a further embodiment of the invention, a two-component mixture is provided for a sprayable concrete mix which is adapted to be applied to a substrate by means of a spray nozzle, one of which components is incorporated in the mixing phase of the cement conglomerate mixture and the other of which components is added to the nozzle, one component comprising a β-naphthalene sulfonate-formaldehyde condensate and the other component comprising a hair (alkylene oxide) soluble in water with a molecular weight (average weight) from 100,000 to 8,000,000, an aluminum-based compound selected from aluminum sulphate, aluminum hydroxide and aluminum hydroxy sulphate being further present in the component that is added to the nozzle.

Further the invention provides a two component blend for use with a sprayable cementitious composition of the type described hereinabove, one component of the blend comprising BNS and the other component comprising PAO and an aluminum-based compound.

Further, the invention provides a two-component blend for use with a sprayable cementitious composition of the type described hereinabove, one component of the blend comprising BNS and an aluminum-based compound and the other component comprising PAO.

For the purposes of this invention, in the case where reference is made to a single material, the possibility of using two or more of such materials is also contemplated. By "cementitious composition" is meant any cementitious composition, such as mortar and cementitious conglomerate. However, the main use of this invention is in the field of "shotcrete" (cement conglomerate capable of being sprayed)

For the purposes of this invention, the term "two-component mixture" refers to a mixture whose two components interact with each other to achieve a result that is not obtained by adding the individual components alone and which consequently is functionally a single blend. In this particular case the individual components are not mixed (indeed they must not be mixed) before adding to the cementitious composition, but are added separately, the second to the nozzle.

PAO suitable for use in this invention can be selected from such materials known in the art. The requirement that the material be water soluble means that the material must comprise at least a high proportion of oxyethylene units. It is preferable that the material is pure poly (ethylene oxide). Furthermore, it is preferable that the molecular weight falls in the range of 2,000,000 to 5,000,000. Typical commercial products useful in carrying out this invention can be found, for example, in the "Polyox" (trademark) range of Union Carbide Chemicals and Plastics. Company, Ine.

BNS for use in this invention is a readily available material widely used as a super plasticizer in the cement conglomerate industry. It can be used as a powder but it is preferred to use an aqueous solution containing approximately 40 per cent active substance in the form of sodium salt.

Interest has recently developed in accelerators comprising aluminum hydroxide, largely due to the fact that their low alkalinity makes conditions at the spray sites more tolerable. Examples of amorphous aluminum hydroxide based accelerators have included mixtures thereof with different water soluble salts. However, it has been found that when the aluminum compounds described herein are used in conjunction with the poly (alkylene oxide) and BNS described herein above, the results are particularly and surprisingly good. For example, it has been found that achieving thick spray layers on walls and ceilings is relatively easy.

In the particular circumstances of this invention, aluminum hydroxy sulfate is often a better accelerator than aluminum hydroxide and is consequently preferred. It is possible to use a mixture of aluminum hydroxy sulfate and aluminum hydroxide and / or aluminum sulfate, but it is preferable to use hydroxy sulfate alone. A typical commercially available hydroxy sulfate is "Gecedral" (trademark) L (from Guilini Chemie GmbH, Ludwigshafen / Rhein, Germany).

It is possible to add one of the two components to the mixture and the other component to the nozzle. The component that is added to the nozzle contains the aluminum-based compound. The components and the aluminum-based compound are preferably added in the form of aqueous solutions or dispersions. While it is possible for the aluminum-based compound to be added separately from the component added to the nozzle, it has been found that better results are achieved when the aluminum-based compound is combined with the component. In this case both are added together as a single aqueous additive. This has the additional advantages of reducing both the complexity of the equipment and the number of materials that have to be handled.

It is preferable to add the BNS to the mixture and the PAO to the nozzle. In this way, the material added to the nozzle is preferably an aqueous solution or dispersion of PAO and an aluminum-based compound.

In a further preferred embodiment of the invention, a super plasticizer is further added to the nozzle in combination with the aluminum-based compound, which is selected from lignosulfonates, melamine sulfonate-formaldehyde condensates and super-plasticizers based on styrene-anhydride copolymer. maleica {"SMA"). SMA-based super plasticizers are preferred and one type of such plasticizers particularly preferred is described in United States Patent 5158 916 and French Application Published 2 672 090, the contents of which are incorporated herein by reference. These are copolymers derived from styrene-maleic anhydride in the form of free acid or salt and are selected from the group consisting of those having the following type and numbers of monomer units:

where M is hydrogen or the residue of a hydrophobic polysiloxane or polyalkylene glycol,

R1, m and n are as previously defined here,

x, y and z are numbers from 1 to 100,

with the conditions that

i) the ratio of x with respect to (y z) is between 1:10 and 10: 1, inclusive,

ii) the z: y ratio is between 5: 1 and 100: 1 e

iii) m n = 15-100.

Although the addition of a super plasticizer at a time when lower versus higher creep is required is not normal, it has been found that the performance of the invention is improved through this addition. When the aluminum-based compound and the component added to the nozzle are included in a single aqueous additive, the super plasticizer is also included in the component. This also has the advantage that less water is needed and that aqueous additive can be more concentrated. Consequently, the invention also provides a process for coating a substrate as previously described herein, a process characterized in that a super plasticizer as previously defined herein is added to the nozzle together with the aluminum-based compound. Also provided is a two component blend as previously described herein, blend characterized in that the component added to the nozzle further comprises a super plasticizer as previously defined herein. This component preferably comprises PAO.

The method of use of the invention is that one component is mixed into the cement conglomerate mixture when it is prepared (before pumping) and the other component of the mixture is added to the nozzle. The substances injected to the nozzle can be injected separately or preferably, as previously described herein, they can be previously mixed and added as a single addition.

The use of the blend of the present invention provides a cementitious composition which is readily pumped but which, when sprayed onto a substrate, forms a poorly readjusting coating, develops strength rapidly and possesses good ultimate strength.

The relative quantities of the substances to be used in the realization of this invention and their relation to the quantity of the mixture of the cementitious conglomerate can be variable within wide limits, to a considerable extent depending on the composition of the mixture, of the desired speed with which the settling properties must be changed and the desired initial and final adjustments. Other factors, such as ambient temperature, can have an effect on the necessary proportions.

With very little experimentation, those skilled in the art can easily determine the appropriate proportions in any given circumstance. As a general guideline, amounts of 0.001 to 0.01 percent by weight of poly (alkylene oxide) and 0.1 to 1.5 percent by weight of BNS (calculated as active substances) will be used, based on the weight of the concrete. The ratio of poly (alkylene oxide) to BNS is 1: 100 to 1:30. When a super plasticizer is employed it is present in 10 to 30 percent, preferably 15 to 25 percent of the aluminum compound (by weight relative to solids). The aluminum compound is present in an extent of 0.1 to 5.0 percent by weight of the cement. The invention is generally applicable to all mixtures of cement conglomerates capable of being sprayed, in cases where a relatively rapid transformation from an initial high setting to a low final setting is required. It is particularly suitable in the creation of permanent final coatings, including the cementitious conglomerate distributed by fiber spray. However, it is also applicable to sprayable thixotropic plaster cement. The invention is further described with reference to the following examples. ; Example 1; A mixture of cement conglomerate capable of being sprayed is prepared by carefully mixing the following components:; Portland cement 450 kg aggregate (crushed stone 1700 kg with a maximum diameter of 8 mm); water 200 kg BNS (aqueous solution at 40%) 1.1 Kg The mixture was fed into the nozzle by spraying. An aqueous dispersion of the following constitution m weight was injected into the mixture: water 69.1 parts polyalkylene oxide ^ 0.025 parts aluminum hydroxy sulphate ^ 25.5 parts super plasticizer based on SMA 5.375 parts 1. "Polyox" WSR 301 by Union Carbide Chemicals; 2. "Gecedral" L from Guilini Chemie GmbH; 3. "Rhec-build" 3520 from MBT, in such a way that 0.02 kg of polyalkylene oxide and 6.9 kg of aluminum hydroxy sulphate were injected per cubic meter of cement conglomerate. The concrete was sprayed onto a compact material in a single pass to provide a 30-40cm layer. This layer has undergone evaluation according to the Guidelines on Shotcrete published by the Austrian Concrete Society, a publication well known to people in the industry. The stabilization was determined by means of the well known Vicat tips and the mechanical strength by means of the cores perforated with a penetrometer. The results were as follows:; initial stabilization 2 min. final stabilization 2 min., 40 sec. strength development; 1 day 12 N / mm ^; 7 days 41 N / mm2; Compressive strength on day 28 compared to an unaccelerated concrete was reduced by 12 percent, a remarkable improvement over the distributed concrete. accelerated spraying by means of the procedures established in the art, in which the loss of strength is variable from 20 to 50 per cent. ; Example 2; Example 1 was repeated using the following aqueous dispersion injected into the nozzle (the materials and proportions used being the same for the rest); water 72.5 parts polyalkylene oxide * 0.4 parts aluminum hydroxy sulphate ^ 22.5 parts super plasticizer based on SMA 0.5 parts The compressive strength showed the same excellent improvement with respect to the prior art.

Example 3

Example 1 was repeated using the following cement mix:

Portland cement 350 kg fly ash 60 kg aggregate 1690 kg BNS 1.5 kg sufficient water having been added to provide a water / cement ratio of 0.5.

The aqueous dispersion described in Example 2 was added to the nozzle so that 0.11 kg of polyalkylene oxide and 5.54 kg of aluminum hydroxy sulfate were injected per cubic meter. The results of the tests were as follows.

initial stabilization 1 min., 20 sec. final stabilization 2 min., 00 sec. resistance development

6 min. 0.35 N / mm2

1 day 18.1 N / mm2

7 days 27.9 N / mmn2

The loss of compressive strength compared to the cementitious conglomerate distributed by non-accelerated spray was 6 percent.

Example 4

The following composition of cement conglomerate distributed by spray on the basis of weight was prepared:

cement 425 Kg / m3 BNS (40% aqueous solution) 1.5%

The mixture had a W / C ratio of 0.48 and a trim of 22 cm and a widening of 53.5 cm.

The mixture was sprayed, the aqueous dispersion of Example 2 having been added to the nozzle.

This was added in a measure of 5 percent solids by weight on the cement.

Compressive strength was measured over time and was as follows:

2 hours 0.9 MPa1

4 hours 1.3 MPa <2>

1 day 15.0 MPa <2>

7 days 0.9 MPa <3>

1. measure with the tip

2. Hilti fit

3. measure in the soul

Example 5

The sprayed concrete mix was prepared as follows:

cement 425 Kg

aggregate (0-8 mm) 1713 Kg

BNS 1.5% by weight The W / C ratio was 0.47, the adjustment was 20 cm and the widening was 51 cm. Single samples of the mixture were dosed with 4 per cent and 5 per cent by weight of solids with respect to the cement of the aqueous dispersion of Example 2 and the compressive strengths were measured by means of the penetration tips. The results are shown in the following table: strength dosage (MPa) measured at celerator 15 30 1 4 6 12 24.

minutes hours

4% 0.5 0.5 0, 6 1, 0 7, 0 14, 0 24, 1 5% 0, 5 0, 5 0.6 1.0 7.0 15.0 29.5

Claims (10)

Claims 1. A process for coating a substrate with a cementitious composition comprising the preparation of a hydraulic cementitious mixture and its application on a substrate by means of spraying through a nozzle, a component of a two-component mixture being added to the mixture. another component being added to the nozzle, the components being a condensate of β-naphthalene sulfonate-formaldehyde and a water-soluble poly (alkylene oxide) with a molecular weight (average weight) from 100 000 to 8000 000, an accelerator being further added to the nozzle which is selected from the group consisting of aluminum sulfate, aluminum hydroxide and aluminum hydroxy sulfate. 2. Process according to claim 1 characterized in that the accelerator constitutes a part of the component added to the nozzle. 3. Process according to claim 1 or according to claim 2 characterized in that the β-naphthalene sulfonate-formaldehyde condensate is added to the mixture and the water-soluble poly (alkylene oxide) is added to the nozzle. 4. Process according to each of claims 1 to 3 characterized in that the accelerator is aluminum hydroxy sulfate. 5. Process according to each of claims 1 to 4 characterized in that a super plasticizer is further added to the nozzle in combination with the accelerator, which is selected from the group consisting of lignosulfonates, melamine sulfonate-formaldehyde condensates and super plasticizers to styrene-maleic anhydride copolymer base. 6. Process according to each of claims 1 to 5 characterized in that the super plasticizer is a super plasticizer based on styrene-maleic anhydride copolymer selected from those having the following type and the following numbers of monomer units: wherein R is a C2-6 alkylene radical Ri is a C1_20 'alkyl group, a Cg..g cycloalkyl group or a phenyl group, x, y and 2; they are numbers from 0.01 to 100, m is a number from 1 to 100 e n is a number from 10 to 100 with the conditions that i) the ratio of x with respect to (y z) is between 1:10 and 10: 1, inclusive, ii) the z: y ratio is between 3: 1 and 100: 1 e iii) m n = 15-100 and those that have the following types and monomer units: where M is hydrogen or the residue of a hydrophobic polysiloxane or polyalkylene glycol R-1, m and n are as previously defined here, x, y and z are numbers from 1 to 100 with the conditions that i) the ratio of x with respect to (y z) is between 1:10 and 10: 1, inclusive, ii) the z: y ratio is between 5: 1 and 100: 1 e iii) ra n = 15-100. 7. Process according to each of claims 1 to 6, characterized in that the relative weight proportions of the condensate of β-naphthalene sulfonate-formaldehyde and of the soluble poly (alkylene oxide) are respectively 0.1-1.5 per cent and 0.001-0 , 01 percent by weight as active substances with respect to the weight of cement, the weight ratio of poly (alkylene oxide) to β-naphthalene sulfonate-formaldehyde condensate is from 1: 1000 to 1:30 and the accelerator is present in a miaura from 0.1 to 5.0 percent by weight of the cement. 8. Process according to each of claims 1 to 7, characterized in that when the super plasticizer is impregnated it is present in the amount of 10 to 30 percent by weight of the accelerator. 9. Two component blend for use with a sprayable concrete mix which is adapted for application to a substrate by means of a spray nozzle, one of which components is incorporated in the mixing stage of the mix of the mix. cementitious and the other of which components is added to the nozzle, one component comprising a condensate of β-naphthalene sulfonate-formaldehyde and the other component comprising a water-soluble poly (alkylene oxide) of molecular weight (average weight) of 100 000 to 8000 000, an aluminum-based compound selected from aluminum sulphate, aluminum hydroxide and aluminum hydroxy sulfate being further present in the component that is added to the nozzle. 10. Two-component mixture according to claim 9 characterized in that one component comprises a condensate of β-naphthalene sulfonate-formaldehyde and the other component comprises a water-soluble poly (alkylene oxide) and an aluminum-based compound selected from aluminum sulfate, aluminum hydroxide and aluminum hydroxy sulfate.